Location: Application Technology Research2014 Annual Report
1a. Objectives (from AD-416):
The overall objective of this project is to conduct research that is relevant to the containerized nursery and greenhouse production (protected horticulture) industry, which will produce outcomes that enhance efficiency, improve economic return, and reduce environmental impact. The following objectives, which have been identified during the past project cycle; have been carefully selected by the Greenhouse Production Research Group to meet priority researchable needs of the industry. Staff and resources have been assembled to address these researchable objectives, and initial research has yielded a base of knowledge, appropriate research skills, and procedures to address this project. Over the five-year planned duration of this project, it is anticipated that there will be significant enhancement of floricultural and nursery productivity with optimization of water, nutrient, fertilizer, and crop protection inputs while minimizing agrochemical, labor, and environmental impacts. Objective 1: Determine the role of silicon in management of abiotic stresses in protected horticulture production systems. Sub-objective 1.1: Elucidate the mode of action of supplemental silicon on the alleviation of abiotic stress symptoms. Sub-objective 1.2: Identify a strategy for supplying supplemental silicon in protected horticulture systems. Objective 2: Determine the influence of environmental parameters on growth and development of protected horticulture crops and incorporate the information into user friendly decision support software such as Virtual Grower. Sub-objective 2.1: Quantify photosynthetic responses of protected horticulture crops to environmental parameters. Sub-objective 2.2: Evaluate energy-efficient lighting and heating strategies for bedding plant production. Sub-objective 2.3: Expand the decision support model Virtual Grower to include additional production parameters and crops. Objective 3: Develop management strategies for containerized crop production systems that improve crop growth, reduce costs, and reduce loss of nutrients and agrichemicals to the environment. Sub-objective 3.1: Quantify the chemical and physical properties of novel materials that provide producers with substrates that are economical, sustainable, and effective. Sub-objective 3.2: Determine the utility of biochar for supplying phosphate and potassium in peat and bark-based substrates. Sub-objective 3.3: Through improved understanding of weed biology, develop methods for weed control in crops and sites where herbicides are not labeled.
1b. Approach (from AD-416):
A multi-disciplinary team will address the goal of enhancing containerized crop production in the context of protected horticulture by utilizing a three-fold approach to address production efficiency, economic return, and environmental impact. Plant nutrition, including the role of silicon as mediated through soilless media composition, will be studied to determine how plant stress is impacted by nutrient supply in both floricultural and nursery crops. Environmental parameters, such as light, temperature, and carbon dioxide, will be evaluated for their influence on growth and development and results will be incorporated into our decision support software model, Virtual Grower. Management strategies will include chemical and physical quantification of substrate components, as well as determination of the utility of novel components as sources of macronutrients in nutrient deficient soilless media, and the improved understanding of weed biology to improve control approaches for crops and sites which lack current herbicide alternatives.
3. Progress Report:
Xenopus expression analysis of the putative silicon (Si) passive transporters from tobacco, tomato and Arabidopsis thaliana is still in progress. All constructs have been cloned into Xenopus Gateway expression vector, pFUT28. Once vectors are linearized, the cRNA will be amplified and expression analysis performed. Nutrient release from slag-amended soilless media was quantified over time using soil extraction columns followed by greenhouse plant trials with tomato and geranium to determine the bioavailability of the released micronutrients. Tissue analysis of plants grown in soilless media with an increasing slag amendment were compared to plants grown in media amended with a known level of micronutrient supplement. Growth chamber studies were conducted and single-leaf photosynthetic curves developed for seven commonly grown species (basil, gaillardia, impatiens, pentas, rudbeckia, sunflower, and zinnia) in response to short-term fluctuations in irradiance, temperature, and CO2. These data will be modeled and the models incorporated in the Virtual Grower decision-support program to help growers manage their crops more efficiently. Five species (angelonia, dianthus, lantana, pansy, and petunia) were evaluated for their ability to withstand periodic temperature and irradiance fluctuations (mimicking energy-efficient conditions) in greenhouse production. Plants were grown in a normal, high-energy use greenhouse and transferred to a cool, low light, energy-efficient greenhouse for 0, 1, 2, 4, or 7 days per week. Exposing angelonia to energy-efficient conditions for a little as 1 day per week resulted in a delay in flowering, whereas delays in flowering in dianathus, lantana and petunia occurred after 4 days per week. No delays in flowering were observed in pansy across all treatments. Flower number, relative chlorophyll content (SPAD), plant width, and plant dry weight decreased in all species as the number of days per week in energy-efficient conditions increased. “Cold sensitive” species were more negatively affected than cold-tolerant species. Periodically reducing greenhouse air temperatures and providing minimal supplemental irradiance may be a viable method to reduce greenhouse energy costs during winter and early spring production. Experiments were conducted to determine the impact of gasified rice hull biochar (GRHB) on Pythium infection of seedling geranium roots. Biochar did not promote nor reduce Pythium infection at inoculum levels used. More research is planned to more narrowly define the Pythium inoculum rate in order to more accurately assess the potential effect of GRHB on root disease. Parboiled rice hulls, torrefied rice hulls, and gasified rice hulls were amended into a typical greenhouse soilless substrate at 10% of the substrate volume. Substrates were packed into glass columns and leached daily to determine micronuturent retention and release. Parboiled and torrefied rice hulls neither retained nor released a significant concentration of micronutrients. Gasified rice hulls released a large concentration of phosphorus and potassium. Additional research utilizing containerized plants is planned to determine if macronutrient release observed in leaching columns can be strategically utilized in greenhouse crop fertilizer programs. Light level penetration of commonly used mulches for container production is being determined. Equipment is being purchased, and experimental apparatus for measuring the light level beneath a mulch layer is being constructed. Once the quality and quantity of light penetrating mulches is established, controlled experiments will be conducted to determine weed response to these levels and qualities of light.
1. Biochar type affects macronutrient retention and release in soilless substrate. Intensive production of containerized crops is sometimes alleged to be a contributor to nutrient release and subsequent contamination of ground water and watersheds which ultimately contributes to algal blooms in lakes and waterways. ARS researchers at Toledo and Wooster, OH have researched and documented the role of biochars, produced from differing feed-stocks, in moderating the release of nutrients (nitrates, phosphate, potassium) from soilless growing substrates. Soilless substrate was amended with 10% biochar, placed into glass columns, fertilized with a standard fertilizer charge, and then leached with clear water repeatedly over a 14-day period. Leachates were collected and analyzed for the nutrient components and compared over time against a non-amended substrate. The biochar types differed in nutrient retention time with each nutrient responding differently, but most interestingly all types provided a net increase in potassium over the initial fertilizer charge. With careful management and use of selected amendments, greenhouse and nursery growers should be able to reduce fertilizer inputs resulting in less nutrient contamination of the environment.
2. Short-term reductions in light and temperature can reduce greenhouse energy costs without reducing plant quality. Energy costs for heating and supplemental lighting are significant expenses in the production of greenhouse ornamentals during winter and spring. ARS researchers at Toledo, OH documented that periodic short-term reductions in temperature and irradiance could reduce energy costs by 10 – 20% without reducing plant quality. Five plant species were grown in a high-energy use greenhouse (at optimal temperatures, with supplemental lighting) and transferred to a low-energy use greenhouse (cool temperatures, no supplemental lighting, and an energy curtain) for one or more days per week. Greenhouse growers and managers can use this research to reduce greenhouse energy costs during winter and early spring production and increase profitability.Bilderback, T.E., Riley, E.D., Jackson, B.E., Kraus, H.T., Fonteno, W.C., Owen, J.S., Altland, J.E., Fain, G.B. 2013. Strategies for developing sustainable substrates in nursery crop production. Acta Horticulturae. 1013:43-56.